Beautiful, well-groomed fingernails are highly valued and, in an aesthetic sense, are the highlight of the hand and enhance a person's overall appearance. On a more utilitarian level, nails shield the ends of the fingers and toes from trauma and serve to protect the delicate sense of touch in the fingertips.
Nails are vestigial remnants of defensive weapons of our distant ancestors. In humans, nails evolved as aids for picking up small objects and for scratching. The nail is a direct outgrowth of the skin. The nails are primarily composed of keratin, the same hard tough protein that also forms the feathers and beaks of birds, the shells of turtles, lobsters, and crabs, the scales of fish, and the claws of animals.
Fingernails and toenails are living tissue. The nail is formed in a pocket of skin that has grown inward and is called the nail matrix. This area generates the nail and is also called the root of the nail. It appears wedge-shaped, with the nail plate fixed at the opening. The outer layer of the matrix contains specialized cells that create the keratin that grows out as the nail plate.
The nail plate is the commonly referred to as a person's fingernail or toenail. It is hard, smooth, shiny, somewhat rectangular, and slightly convex. The plate is translucent and essentially colorless, but appears pink because of the network of blood vessels under the nail bed below the nail plate. The nail plate grows as if in a 3-sided tunnel with no roof.
The nail bed is the finger tissue or toe tissue that supports the nail. The nail bed does not contribute to the outward growth of the nail but does supply necessary nutrients to the nail plate. The surface of the nail bed has vertical ridges and depressions that interlock into the nail plate to give a firm adhesion between the nail bed and the nail plate. The nail bed grows out along with the nail plate, and its elaborate network of blood capillaries help provide nutrition for the nail plate. When the nail plate is separated from the nail bed such as after an injury, the nail plate becomes discolored, cloudy and distorted.
Nails grow continuously throughout a person's life, growing approximately one-half to one millimeter weekly. For the nail plate to completely replace itself, from the time it is formed at the root until it reaches beyond the fingertip, takes from 5 to 7 months. Toenails grow much more slowly, about one-third to one-half the growth rate of fingernails.
In children, the rate of nail growth is high, and they have fingernails that are thick, strong, and smooth. But as individuals reach adulthood, this rate diminishes and nails become more fragile and possess a less smooth surface. Furthermore, injuries, stresses and the effects of human aging can weaken and thin nails, leading to premature breakage and tearing. Damage to the nails can also increase the incidence of fungal and bacterial infections of the nail bed and cuticles. Likewise, exposure of nails to harsh chemicals and alkaline conditions also weakens nail integrity. Nail polish removers also can cause nail damage. Such polish removers usually contain 98 percent to 100 percent acetonitrile or acetone, chemicals that can cause nail damage even after brief exposure. Another major source of nail damage is caused by the attachment of plastic artificial nails (cosmetic nails) over the true natural nail. The glues and adhesives used for attachment often severely weaken and thin the natural nail.
The treatment of fingernail and toe nail problems such as poor growth, lack of thickness and strength, lack of smoothness and tendencies to tear remains a major problem despite the development of numerous treatments such as the use of nail hardening polishes, protein elixirs such as bovine collagen emulsions, various types of wearable protective fingernail covers and so forth. The problem with current techniques for improving nail health is that they all are poorly effective, time consuming, and expensive when performed in nail salons.